A local government official told the AFP news agency that he was on the scene. "The Islamists took the unmarried couple to the center of Aguelhok. The couple was placed in two holes and the Islamists stoned them to death," he said.

"The woman fainted after the first few blows," he said. The man shouted out once and then was silent, he added.

Most people living in northern Mali have long practiced Islam, but frustrations with the strict form of shariah being imposed by Islamists have sparked several protests in recent months.

Ansar Dine and well-armed allies, including al-Qaida splinter group MUJWA, have hijacked a separatist uprising by local Tuareg rebels and now control two-thirds of Mali's desert north, territory that includes the regions of Gao, Kidal and Timbuktu.

Western and African governments are struggling to muster a response to the crisis as politicians in the capital Bamako continue to squabble over how the country should be governed after a March coup removed the country's president.

In the first installment of Rock Center's Hidden Planet series, Richard Engel travels to Mali, on the edge of the Sahara desert, to discover the city of Timbuktu.